add 'ldd' to cross-tools ?

[Jilles Tjoelker]

On Wed, Jan 04, 2012 at 11:58:15PM +0100, Luigi Rizzo wrote:
> On Wed, Jan 04, 2012 at 02:30:27PM -0800, Garrett Cooper wrote:
> > On Wed, Jan 4, 2012 at 2:29 PM, Luigi Rizzo <rizzo at iet.unipi.it> wrote:
> ...
> > >> $ objdump -x `which tar` | awk '$1 == "NEEDED" { print $2 }'
> > >> libarchive.so.5
> > >> libbz2.so.4
> > >> libz.so.6
> > >> liblzma.so.5
> > >> libbsdxml.so.4
> > >> libcrypto.so.6
> > >> libc.so.7

> > > wonderful, thanks!

> >     Np! The only gap with both of these tools is that you have to
> > watch out for dl_open'ed binaries as they won't show up in ldd/objdump
> > -x. If I could figure out how to detect these with a command line
> > tool, I would be set for life :).

> and the other thing, i just realized, is that once you locate
> the libraries you should run objdump recursively to find
> out further dependencies. Perhaps ldd sorts this out by itself ?

ldd basically sets LD_TRACE_LOADED_OBJECTS=yes and runs the program
(after having checked it is a dynamic executable). This means it will
not work as a cross tool. Upsides are that it is simple and it shows
exactly what rtld would do (because it is rtld), handling things like
/var/run/ld-elf.so.hints, LD_LIBRARY_PATH and pathnames hardcoded into
objects.

You will have to run objdump (or readelf) recursively. (Note that there
are also use cases where just the non-recursive NEEDED tags are
appropriate, not all objects that happen to be loaded.)

-- 
Jilles Tjoelker